Wow, that's news to me. But seriously, it's incredibly expensive. For a "plain" buspowered USB drive, let's say an ICY case and a 500 GB (5400 RPM) quality drive, I'll pay like 100 Euros quid.
Anyway, I think that for your endeavours, a FW800 case with a proper drive in it would be the best choice, leaving one of the rare USB ports free for other things (MIDI keyboards, mice, data sticks, etc.).